1. Field of the Invention
The present invention relates generally to a reinforcement structure of safety helmet and a manufacturing method thereof. In the manufacturing method of the reinforcement structure, a cushion (foam) material is injected into a molding module to form a helmet body enclosing a helmet-shaped structure body. The helmet body and the structure body are combined to form an integrated complex reinforcement structure as a helmet assembly, which is easier to manufacture and has higher structural strength, lighter weight and higher security.
2. Description of the Related Art
A conventional safety helmet is manufactured in such a manner that a plastic shell is fixed in a vacuum molding device and a foam material is injected into the molding device and heated to form an anti-impact filling body tightly enclosed by the plastic shell to achieve the safety helmet. For example, U.S. Pat. No. 4,466,138 discloses a safety helmet with a shell injected from thermoplastics and method for the manufacture of said helmet. Another prior art discloses a manufacturing method of a safety helmet.
The external plastic shell of the conventional safety helmet serves to resist against the impact and thrust force of a sharp article. Moreover, the plastic shell encloses and holds the foam filling body, which is relatively crackly. Accordingly, when impacted by a strong external force, the plastic shell can buffer the impact force and avoid breakage of the foam filling body so as to ensure safety.
In the conventional foam cushion material, each foam filling body is a closed structure body. During the heating process, the borders of the adjacent foam particles are restricted by the mold to irregularly tightly attach to and bond with each other. When impacted by an external obtuse force, the irregularly tightly bonded foam particles can absorb the impact force and spread the impact force in all directions. However, when the foam filling body is severely impacted by a sharp object, the sharp impact force is likely to act on the borders of the foam particles to separate the borders from each other and break the foam filling body apart. Under such circumstance, the anti-impact performance and buffering effect of the foam particles are deteriorated and it is impossible for the foam particles to effectively uniformly spread the impact force to the respective parts of the helmet body (or the foam filling body).
Especially, when the conventional helmet structure bears a lateral impact or pressure, the lateral action force or pressure will create a bending shear force applied to the helmet body. The bending shear force will damage the helmet body, which is simply enclosed in the plastic shell on single side. As a result, a wearer's head can be hardly perfectly protected.
Therefore, in the prior art, the external plastic shell is strengthened (thickened) to increase the resistant force against the impact of the sharp object and the lateral impact. The plastic shell also encloses and holds the cushion foam material (or the foam filling body) to prevent the cushion foam material from breaking under impact. However, when the thickness and weight of the plastic shell and/or the cushion foam material are continuously increased under high security requirement, the thickness and volume of the entire safety helmet are increased to increase the load on a wearer.
In order to overcome the above problem, an improved helmet has been developed. In this helmet, a layer or multiple layers of fiber to help in reinforcing the foam filling body against the impact of sharp objects. However, as well known by those who are skilled in this field, it is relatively troublesome and unstable to manufacture such helmet. Moreover, the fiber layer also will lead to increase of the total weight of the helmet (including the helmet body). Furthermore, the fiber layer structure lacks in self-support ability. As a result, in the case that a heavy pressure (especially a lateral pressure) or an impact force in different form is applied to the helmet, the helmet can hardly bear the impact.
According to the above, even with the fiber layer, the conventional helmet still fails to have sufficient strength against an impact force in different form. Therefore, the helmet can hardly protect a wearer from lateral impact. In the case that the security is enhanced simply by means of thickening the plastic shell or the foam filling body, the volume and weight of the entire safety helmet will be inevitably increased to increase the load on a wearer. This is not what we expect.
In tests and practical use, it is found that the conventional safety helmet structure has some problems. It is necessary to redesign the assembling structure of the external plastic shell and the internal foam filling body so as to enhance the structural strength of the helmet and increase the security thereof. Moreover, it is necessary to facilitate the manufacturing process of the conventional safety helmet and change the transmission force of the external impact force (or external action force) to increase the support ability thereof for providing full protection for a wearer.
For example, the external impact force can be uniformly spread to the respective parts of the entire helmet body through the internal structure body (or the foam filling body). In this case, the structure body can uniformly bear different forms of impact. Also, it is necessary to thin the external plastic shell or remove the fiber layer so that the helmet body can have higher structural strength in all directions or sections. In this case, the safety helmet can fully bear the external impact or lateral impact pressure. Moreover, the weight of the helmet can be reduced without deteriorating the security. This widens the application range of the safety helmet.